In order to stabilize soil and rock formations, it is known to utilize soil nailing in which a plurality of elongate reinforcing members are driven into the ground in an array in order to improve the bulk properties of the surrounding soil and rock.
One reference that discloses a device and method of soil nailing includes the U.S. Pat. No. 5,044,831, the disclosure of which is hereby incorporated by reference.
Two additional examples of references that disclose soil nailing techniques includes the British Patent No. 1,580,142, and the European Patent 0 239 258.
While these references may be adequate for their intended purposes, there is still a need to provide an improved soil nailing device that is easier to maintain, as well as one that is more efficient by having the capability to launch a greater number of soil nails over a period of time.
The portion of the soil nailing device that contacts the ground when a nail is being launched is referred to as the shroud or baffle assembly which enables the distribution of pressure away from the barrel of the launcher, and also captures any fragments that are carried through the barrel, such as the sabot or collett which is attached to the distal tip of the soil nail. As time progresses, the baffle may become clogged with soil or other debris, thereby limiting its ability to effectively release high-pressure from the barrel. The baffle may become damaged over time, thereby also changing it pressure-relieving characteristics. The failure to consistently relieve pressure from the barrel as the nail is launched can negatively affect the depth of the launched nail. Therefore, there is a need to provide an improved design for the baffle to ensure it captures fragments launched from the barrel, yet allows effective pressure release from the barrel.
Another disadvantage of existing soil nailing devices is that it may take an inordinate amount of time to pressurize the device so that a nail can be launched. One type of soil nailing device includes a barrel having a coaxial arrangement of an inner tube/casing and an outer tube/casing. The annular space between the inner and outer tubes is pressurized, and supplies the motive force for launching the soil nail by release of pressure within this annular space into the breach of the barrel. This annular space is pressurized by a source of compressed gas. Preferably, the source of compressed gas includes a plurality of pressurized containers that are stored on a deployment vehicle that transports and secures the launching device. One limiting factor in how quickly soil nails can be launched depends upon the time in which it takes to adequately pressurize the annular space for the next nail to be launched. Because of the noise associated with the launching of a nail, safety requirements for construction along highways and other roads generally require that traffic be stopped during the launching of a nail. The more quickly the soil nails can be launched, the less disruption for traffic flow and of course the more quickly a job can be completed. Therefore, there is also a need to provide a soil nail launching device that has a shorter cycle time in terms of the number of soil nails that can be launched in a period of time.
Additionally, there is also a need to reduce the required pressure to launch a nail, yet still achieving the same depth of penetration for a soil nail that is launched. A reduced pressure requirement will inherently reduce the time to launch successive nails.